By Vibhuti Sharma and Arjun Panchadar

(Reuters) - Tesla Inc Chief Executive Elon Musk was filmed smoking marijuana and wielding a sword on a webcast, just hours before the automaker said its recently-appointed accounting chief would leave, the latest in a string of unusual behavior and executive departures that have stunned investors.

Shares of the electric carmaker tumbled more than 6 percent on Friday to $263.24, with investors on edge after a tumultuous August during which Musk proposed and then abruptly pulled the plug on a go-private deal.

Chief Accounting Officer Dave Morton resigned after just one month in the job because of discomfort with the attention on the company and pace of work during that time, Tesla said in a filing on Friday. It later said that Chief People Officer Gaby Toledano would not return from a leave of absence, just over a year after joining.

Later on Friday, Tesla named a new president of automotive operations, promoting eight-year Tesla employee and former Daimler truck exec Jerome Guillen into the role overseeing all automotive operations and reporting to Musk.

That move, described in a company blog with several other promotions as a result of board and management discussions, gives Musk a seasoned auto industry veteran to lean on at a time when some investors have called for a new chief operating officer. Shares barely moved after hours, when the promotions were announced.

Morton and Toledano, whose departures come shortly after the U.S. Securities and Exchange Commission opened an inquiry into Musk's aborted privatization plan, join dozens of senior executives who have left Tesla.

"Since I joined Tesla on August 6th, the level of public attention placed on the company, as well as the pace within the company, have exceeded my expectations. As a result, this caused me to reconsider my future," Morton said in the filing.

Late on Thursday, Musk was filmed drinking whiskey, briefly smoking marijuana and wielding a Samurai sword during a 2-1/2-hour live Web show with comedian Joe Rogan that swiftly spread across social media.

Taking a puff from a joint, which Rogan said was a blend of tobacco and marijuana and legal in California, Musk said he "almost never" smoked.

"I'm not a regular smoker of weed," Musk said. "I don't actually notice any effect ... I don't find that it is very good for productivity."

It was the latest in a string of unconventional behavior by the billionaire South African native who is also CEO of rocket startup SpaceX.

Even before Musk's surprise Aug. 7 tweet that he had funding "secured" for a go-private deal, Tesla had been under scrutiny from investors, analysts and short-sellers as it works to hit production targets and slow its cash burn.

Morton, who is walking away from a $350,000 base salary and a $10 million new-hire stock grant that would vest over four years, said he believed "strongly" in Tesla and that he had no disagreements with the company's leadership or its financial reporting.

Analysts on Friday reiterated their call for Tesla to bring in another senior leader.

"We have been calling for a co-CEO or COO to assist to codifying the leadership structure and in so doing, the culture at Tesla," said James Albertine, analyst at brokerage Consumer Edge, speaking before the promotions were announced.

"We think this is further evidence that the time is now for management and the board to address these issues."

SOBERING EFFECT ON INVESTORS

Tesla's $1.8 billion junk bond maturing in August 2025 plunged as much as 4 cents on the dollar to below 82 cents, a record low, in Friday trading, pushing the yield above 8.8 percent.

Coupled with an upfront cost of 21 percent of insured value, it now costs an investor around $280,000 to insure $1 million of Tesla debt for a year.

With Tesla's stock falling to its lowest level since April, short sellers added 810,000 shares to their positions, bringing the total as of Thursday to about 32.6 million shares, according to S3 Partners, a financial technology and analytics firm.

Tesla has told investors it expects to turn a profit in the second half of this year, a forecast the company's head of investor relations, Martin Viecha, reiterated at a conference earlier this week sponsored by RBC Capital Markets, RBC analyst Joseph Spak wrote in a note on Thursday.

Viecha also restated Tesla's forecast that it will build 50,000 to 55,000 of its Model 3 sedans in the current quarter, and indicated the company's working capital will improve as production increases, Spak wrote.

Prominent short-seller Andrew Left has sued Tesla and Musk, saying in his proposed class-action complaint on Thursday that Musk's issuance of materially false and misleading information related to his abandoned plan harmed both short-sellers and those hoping the stock would rise.

(Reporting by Nivedita Balu and Ismail Shakil in Bengaluru, additional reporting by Noel Randewich in San Francisco, Joe White in Detroit and Dan Burns in New York; Writing by Meredith Mazzilli; Editing by Matthew Lewis and Rosalba O'Brien)